How Angry? Calculating Crowd Size in Taiwan

Protesters gather with banner reading “condemn the violent government!” while during a massive protest over a controversial China-Taiwan trade pact in front of the Presidential Building in Taipei, Taiwan, Sunday, March 30, 2014.

Associated Press

As the dust settles from a massive demonstrationin Taipei on Sunday against a trade pact between China and Taiwan, there continues to be wide disagreement over how many people were actually there.

The police put the peak size of the crowd at more than 116,000 people. The protest organizers estimated as many as half a million took part, which they say might make it the largest demonstration to date on an island that is perennially demonstrating.

Disagreement between authorities and organizers over the size of protests is common around the globe, but such a wide disparity made us wonder: How, exactly, does one go about estimating large crowds?

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In a press release issued late Sunday, the Taiwanese government said police used what is known as the Herbert Jacobs method. Named for a journalist who taught at the University of California’s Berkeley campus during the protest-happy 1960s, this formula involves calculating the surface area of the streets occupied by protesters, then multiplying by an estimate for crowd density based on rules of thumb developed by Mr. Jacobs.

The journalist developed the guidelines – now used by police departments across the U.S. — by drawing grid lines on aerial photographs of the main protest square, Berkeley’s Sproul Plaza, and counting the number of people per square using a magnifying glass. After comparing multiple photographs, he found that a loose crowd will have 10 square feet of space for each person, where a more tightly packed crowd has 4.5 square feet per person. In a suffocating crowd – think in front of the stage a rock concert — each person occupies around around 2.5 square feet.

A protester displays a banner supporting Taiwan during the protests.

Associated Press

Like Mr. Jacobs, student organizers in Taipei also used overhead photos, though they were somewhat less precise in analyzing them. According to Chen Rui-Guang, a representative of the protesters, students compared images of Sunday’s protest to those of the “Red Shirt” protests in 2006. Police had said that those protests drew 360,000 at their height, while organizers claimed the number was more than one million.

“We came to our estimate through observations on the scene and by comparing the pictures to previous protests,” Mr. Chen said. “We believe this is the biggest protest in Taiwan’s history.”

While the police approach is more systematic, the Jacobs method has its limits. Estimating the crowd density is difficult as crowds are not usually uniform.

Based on the surface area of the streets involved in Sunday’s gathering, its seem unlikely that half a million people showed up. There simply isn’t enough space for that many people. But there are reasons to doubt the government number as well: A police official told China Real Time the official estimate only included the main streets because it was impossible to tell if people in other places were part of the protest or just onlookers.

Even if only a fraction of those occupying the side streets were protesters, than 116,000 is likely too low.

For its part, the Associated Press estimated Sunday’s crowd size at 200,000. That’s not a mind-blowing number in Taiwan. But, for authorities in Beijing and Taipei, it’s not an insignificant one either.

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